WASD - To move! Use mouse to aim and shoot.
_ Aim for the brains!
_ Reload only when necessary (otherwise lose the bullets inside the magazine you are discarding).
_ underestimate the Pistol. It can kill a zombie with two head shots and faster to reload.
_ Use the Pistol whenever possible, and use the stronger weapons when the enemies are too many.
_ The grenade excels when there are lots of zombies together.
_ With the shotgun, you can hit two zombies in one shot, provided they are far away (because the bullets/pellets disperse).